An Analysis of VDOT’s Sight Distance Requirements Relative to Context-Sensitive Designs

About the report:

Intersection sight distance (ISD) requirements are intended to enhance safety by ensuring visibility at intersections. However, in dense urban areas, these requirements can preclude elements of the urban streetscape, such as street trees, on-street parking, and transit infrastructure, and can restrict compact mixed-use developments, such as traditional neighborhood developments. Although literature on the safety impacts of ISD is plentiful, little of it is tailored to low-speed urban environments, an area of interest to the Virginia Department of Transportation (VDOT). Accordingly, this study examined the existing state of practice on ISD guidelines and conducted a safety analysis focused on low-speed urban intersections. This report first reviews literature and policies across state departments of transportation (DOTs) and localities. Second, it presents findings from a survey of 17 state DOTs, 34 Virginia localities, and 24 VDOT residencies on current practices related to implementing ISD standards. Then, it provides details of a safety analysis examining how ISD impacts crash occurrence for 359 intersections in Virginia, distinguishing between T-intersections and four-leg intersections and stratifying by speed ranges (low speed ≤ 25 mph and high speed ≥ 30 mph).

Although most state and local agencies align their ISD requirements closely with the American Association of State Highway and Transportation Officials’ Green Book guidelines, variations appear in their application regarding design flexibility, multimodal considerations, and obstructions. About one-half of the state DOTs have provisions for design exceptions or waivers when ISD requirements cannot be met. Roughly one-third of state DOTs provide multimodal guidance, with limited consideration given to ISD guidelines specific to traditional neighborhood developments. In Virginia, most localities follow VDOT guidance directly, with only a few reporting modified standards. Localities are more involved in development plan approvals and tend to enforce ISD more strictly for new developments, although enforcement is less consistent in older or constrained areas. Residencies noted that ISD-related recordkeeping is often informal or inconsistent, but many reported encountering intersections, especially in older downtown areas, where ISD was not met, and about one-half expressed safety concerns at such locations.

Negative-binomial regression using 2020–2024 Virginia crash data shows that limited sight distance to the right, which is needed for left turns, correlates with higher crash counts for both T-intersections and four-leg intersections, particularly on low-speed roadways. Meeting ISD guidance set by VDOT is negatively correlated with crashes. For intersections with posted speeds less than or equal to 25 miles per hour, increasing sight distance to the right by 100 feet reduced crashes by approximately 9.24% at T‑intersections and 15.8% at four‑leg intersections on average. Crash cost analysis showed potential average annual savings of approximately $1,683 per T-intersection and $3,100 per four-leg intersection for each additional sight distance leg meeting VDOT’s threshold at an intersection. These findings confirm that maintaining adequate sight distance to the right provides a clear safety benefit and that compliance with VDOT sight-distance standards is associated with fewer crashes.

_{Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.}

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